The method for electrically predrying a blank of a ceramic raw mixture is known per se and is used in particular in the production of porcelain insulators of a wide variety of dimensions, in order to bring the clot that is obtained after the extrusion in the form of a clay column to the reduced residual moisture that is necessary for a subsequent shaping operation by turning on a lathe. For this purpose, the still moist clot is connected as an electrical resistance into an alternating current circuit. The alternating current flowing through has the effect of heating up the clot, whereby water is driven out to the extent that the residual moisture necessary for the shaping operation is achieved. After the electrical predrying, the cylindrical clot, which may have a length of several meters and a diameter of over 50 cm, is further processed by turning on a lathe for shaping the inner and outer contours.
In comparison with air drying, electrical predrying significantly reduces the time for drying the clots to the state in which they are ready for turning on a lathe. The reduced time that the clots spend in the drying process allows the overall production throughput to be increased. However, a considerable amount of additional energy is required for the electrical predrying, and the aim is to reduce this further in the interests of cost-effectiveness and environmental protection.